The wt_txn_commit operation is getting stuck in the cache eviction worker and causing timeouts in the MongoDB concurrency tests. The build failure for this ticket is for 4.2, but the failure signature has previously been reported in 4.4 (see BF-15064).

This failure seems to happen most often on the PPC & zSeries machines, but there's a Linux failure in BFG-712263 where you can spawn a host.

WT-6507 might be relevant here.